JPS63106942A - Optical disk - Google Patents

Abstract

PURPOSE:To improve recording and reproducing characteristics by forming a recording layer by sputtering a target made of an indium-antimony alloy. CONSTITUTION:The recording layer 6 which is held in place between dielectric layers 4 and 8 is disposed on a substrate 2. A protective film 10 is formed on the dielectric layer 8. The recording layer 6 is formed of an In-Sb alloy and is formed on the dielectric layer 4 by sputtering the target made of the In-Sb alloy. The compsn. of the recording layer consisting of the In-Sb alloy can be controlled with high accuracy of + or -0.5% in the case of forming said recording layer by sputtering in the above-mentioned manner. The recording layer 6 consisting of the In-Sb alloy is so formed that the alloy compsn. thereof is maintained in a 35-45atom% In range.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) This invention records and erases information by reversibly changing the optical characteristics of a recording layer by irradiation with a light beam such as a laser beam. The present invention also relates to an optical disc that reads the optical characteristics and reproduces information.

(Prior Art) Optical discs have recently attracted attention as large-capacity memories, and optical discs that can be written only once have already been put into practical use for document files and the like.

On the other hand, some erasable optical discs have entered the stage of practical use, but there are problems with product instability.

That is, there are two types of erasable optical disks: magneto-optical and phase-change types. Among these, phase-change optical disks include those that use semiconductors such as TeSGe and TeGe as recording materials. These semiconductors can take two states, crystalline and amorphous, and the complex refractive index Nmn-1k upon irradiation with light differs depending on the state of this phase (J,
orNon-Crystallnc 5o11d
41 (1970)) o Utilizing this, an idea has been disclosed to create an optical memory by reversibly causing a phase change between crystalline and amorphous through heat treatment with a laser beam (M etallurgic
alT transactions 2 G41 197
1) , T e , G e .

A thin film of a semiconductor material such as TeGe has the property that it becomes amorphous when heated to a molten state and cooled at a high speed, and becomes crystalline when heated to a low temperature and slowly cooled.

The amorphous state and the crystalline state have different complex refractive indices and exist stably. However, when these semiconductors are formed into thin films, they have a drawback that they have low chemical stability and gradually corrode in the atmosphere, resulting in deterioration of their optical properties.

On the other hand, as phase change recording materials, there are materials such as InSb that record information through a phase change between two different crystals. In other words, when an InSb film is formed by vapor deposition, the film is amorphous immediately after vapor deposition, but this I
The nSb film is melted and slowly cooled by irradiation with relatively long pulses of high-intensity laser light to form fine-grained crystals, and by irradiation with high-intensity but short pulses, coarse-grained crystals are formed. Information is recorded and reproduced based on the difference in complex refractive index due to the difference in crystal state. In this case, InSb is chemically stable, for example, even if it is left in a harsh environment with a temperature of 70°C and a humidity of 85%.
No deterioration of the recording film occurs for more than one month.

(Problems to be Solved by the Invention) Incidentally, it is known that the recording and reproducing characteristics of the recording film of this In-5b alloy vary depending on the composition of the alloy.
It is difficult to control the composition of an In-5b alloy thin film formed by vapor-depositing an alloy ingot, and compositional variations of ±55 atoms or more easily occur. For this reason, there are drawbacks such as large variations in optical disk products and low yields.

The present invention was made in view of the above circumstances, and has the ability to easily control the composition to the most preferable composition in terms of optical properties, has excellent recording and reproducing properties, and has a stable high yield. The purpose of the present invention is to provide an optical disc that can be manufactured.

[Structure of the Invention] (Means for Solving the Problems) An optical disc according to the present invention is an optical disc in which information is recorded and erased by causing a change in optical characteristics in the recording layer by irradiating the recording layer with a light beam. is characterized in that it is formed by sputtering a target made of an indium-antimony alloy.

(Operation) In this invention, an In-5b alloy recording layer is formed by sputtering an indium (In)-antimony (Sb) alloy target. Therefore, the composition of this recording layer can be determined with high precision (for example, ±0.5%).
) can be controlled to a predetermined composition. Therefore, an optical disk whose recording layer has an optimal composition in terms of recording and reproducing characteristics can be manufactured stably and at a high yield.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a sectional view showing an optical disc according to an embodiment of the invention. The substrate 2 is made of organic resin such as PMMA or polycarbonate, and has a recording layer 6 sandwiched between dielectric layers 4 and 8 . Dielectric layer 8
A protective film 10 is formed thereon. dielectric layer 4,
8, when the recording layer 6 is irradiated with a laser beam,
This is provided to prevent holes from forming in the recording layer 6. On the other hand, the protective film 10 is for preventing the formation of eaves during handling of the optical disc, and can be formed of ultraviolet curing resin or the like.

The recording layer 6 is made of an In-3b alloy and is formed on the dielectric layer 4 by sputtering a target made of an In-8b alloy. In this way, when the In-5b alloy recording layer is formed by sputtering, its composition can be controlled with high accuracy of ±0.5%.

The In-5b alloy recording layer 6 has an alloy composition of 3 In
Preferably, the content is in the range of 5 to 45 at.%. According to the research results by the inventors of the present application, the In-5b alloy recording layer 6 exhibited excellent recording and reproducing characteristics in such a composition range.

The In-5b alloy of the sputtering target is usually
It is manufactured by sintering the powder and then hot pressing the sintered body. Although the filling rate of the target changes depending on the conditions of this hot pressing, it is preferable that the filling rate of the target is 90% or more in view of the recording/reproducing characteristics of the recording layer obtained by sputtering.

Next, a sputtering apparatus for manufacturing an optical disk according to an embodiment of the present invention will be described. The inside of the chamber 21 is connected to an appropriate vacuum pump (not shown) via an exhaust boat 28, and this vacuum pump supplies air to the chamber 2.
1 is evacuated to a vacuum of 10-6 torr. Ar gas or the like is introduced into the chamber 2'1 via a gas introduction boat 29. The base 22 is suspended vertically from the top plate of the chamber 21, and is driven to rotate as shown by the arrow. An optical disc substrate 2 is attached to the lower surface of the base 22.

Two stands 32 and 33 are arranged in the chamber 21, and a target 24 is placed on these stands 32 and 33, respectively.
and 25 are placed. The targets 24 and 25 are connected to external high frequency power supplies 30 and 31, respectively. Shutters 26 and 27 are provided near the areas directly above the targets 24 and 25, respectively.

When forming an optical disk using such a device,
First, 5i02 is used as the target 24, and In40S with a filling rate of, for example, 96% is used as the target 25.
B60 sintered alloy is used.

Further, as the substrate 2, a disc-shaped polycarbonate resin plate is used. After the chamber 21 is evacuated to 10 −6 Torr, the base 22 is rotated at, for example, 60 rpm. Next, Ar gas is introduced into the chamber 21 via the gas introduction boat 29 at a flow rate of IOSCCM, and the Ar gas pressure in the chamber 21 is adjusted to 5111 Torr.

With the shutter 27 closed, the high frequency power sources 30 to 13
．． A high frequency power of 500 W at 56 MHz is applied to the 5i02 target 24 to generate a high frequency plasma discharge.

After performing pre-sputtering for about 2 minutes, the shutter 26 is opened to start forming a film of 5i02 on the substrate 2. Continuing plasma discharge for about 5 minutes, 700 people's 5i0
After forming the second dielectric layer 4, the shutter 26 is closed and the discharge is stopped.

Next, a high frequency power of 80 W is applied from the high frequency power supply 31 to the In4gSb6g alloy target 25, and after pre-sputtering for about 2 minutes, the shutter 27 is opened to form the In40Sbao recording layer 6.

750 rn40sb60 with plasma discharge for about 5 minutes
After forming the recording layer 6, the shutter 27 is closed and the power source 3 is turned on.
Turn off 1.

Next, a high frequency power of 500 W is applied to the 5i02 target 24 again to form 700 5i02 dielectric layers 8.

Thereafter, the inside of the chamber 21 is flushed with N2 gas, and then the sample is taken out into the atmosphere. Next, this sample was spin-coded with an ultraviolet curable resin to a thickness of about 3 μm using a spinner, and then ultraviolet rays were irradiated to cure the resin.

The optical disc formed in this way has its recording layer 8
The composition matches the target composition with high accuracy. For example, when forming a film under the above conditions, the composition In50Sb50. I
n455b55゜1n35 Sb65, In30 S
b7 (Even in a recording layer formed by sputtering using a sintered alloy such as 1 as a target, ±
They agreed with an accuracy of 0.5 at.%.

The dynamic characteristics of the optical disc manufactured in this way were measured using a table rotating type disc evaluation device. First, before recording and erasing, the rotation speed is 60 Orp.
While rotating the disk at speeds of m, a continuous laser beam of 9 mW with a wavelength of 330 nm was irradiated onto the disk to perform initial crystallization. For this initialized optical disk, the board 2
From the side, the DC component was 30 laV DC in voltage.

In this way, for the initialized optical disk, the output was 15 mW, the pulse width was 200 ns, and the duty ratio was 50.
% laser light was irradiated and the signal was recorded. Then,
When a signal is read out from this recording bit 12 using the above-mentioned readout laser beam, the signal is 200 mV with respect to the DC component.
AC signals were obtained. Furthermore, similar to the initialization, 9mW
When the signal of recording bit 12 was erased with continuous light, this alternating current signal was completely erased.

Next, when a sintered alloy is used as a target, the results of a dynamic characteristic evaluation test regarding the influence of the filling rate on the recording and reproducing characteristics will be explained. The composition of the target is In5o 5bsos In455b55゜Into
5b80% Inas 5bss, and In3oSb
7o, and for each composition, samples were prepared in which the filling rate of the sintered alloy was changed to 85%, 9096.92%, and 96%.

Regarding this sample, signals were recorded, reproduced, and erased under the same conditions as described above, as shown below.

Rotation speed: 600 rpm Laser wavelength: 830n11 Initialization and erasure: Continuous optical recording of name W: 15 mW, 200 ns, duty 50% As a result, the read AC signal components (In'w/l are shown in Table 1 below) Shown below.

Table 1 As is clear from this Table 1, the composition of the target is I
The atomic % of n is 35 to 45%, and the filling rate is 90
% or more, the recording and reproducing characteristics are excellent as an erasable optical disc. For this reason, In-5b
As a target for forming the alloy recording layer, it is preferable to use a target having an In atomic % of 35 to 45% and a filling rate of 90% or more. Note that when the signal was erased from the recording layer thus formed using continuous light of 911 W, the signal completely disappeared.

[Effects of the Invention] According to the present invention, the composition of the InSb alloy recording layer can be made to match the composition optimal in terms of its optical characteristics with high precision. Therefore, it is possible to stably manufacture an optical disk with excellent recording/reproducing/erasing characteristics at low cost.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an optical disc according to an embodiment of the present invention;
FIG. 2 is a schematic diagram showing a sputtering apparatus used for its manufacture. 2; Substrate, 4, 8; Dielectric layer<6; Recording layer, 10; Protective film, 21; Chamber, 24.25; Target, 26.
27; shutter, 30, 31; power supply.

Claims (3)

[Claims] (1) In an optical disc in which information is recorded and erased by causing a change in the optical characteristics of the recording layer by irradiation with a light beam,
An optical disc characterized in that the recording layer is formed by sputtering a target made of an indium-antimony alloy. (2) The optical disc according to claim 1, wherein the recording layer formed of the indium-antimony alloy contains indium in an amount of 35 to 45 atomic percent. (3) The optical disk according to claim 1, wherein the target made of the indium-antimony alloy is a sintered alloy with a filling rate of 90% or more.